FACTORS AFFECTING THE WISCONSIN MASTITIS TEST1

Abstract

The influence of chemical sanitizers, lysozyme, DNAase, storage time and temperature, hydrolytic rancidity, and heat treatment on the Wisconsin Mastitis Test (WMT) was studied. Concentrations of 25 to 50 ppm of iodophor and quaternary ammonium compound sanitizers caused significant reductions in WMT values. The test was not affected by chlorine, chloramine-T; or an acid sanitizer. The WMT reaction was completely destroyed by 12.5 μg or more of DNAase/9 ml of milk. Significant decreases in WMT values occurred after storage for longer than 24 hr and the rate of decline increased when storage temperatures above 4.5 C were used. Lysozyme concentrations of 50 to 200 μg/100 ml of milk decreased the rate at which the WMT values declined during storage. The test values were not affected by increases in acid degree values. Heat treatments greater than 43 C for 1 min caused severe reductions in WMT values. The effect increased as the severity of the heat treatment was increased.